0038-【Linux系统】-ubuntu18.04无法输出"（" 问题，解决方法

系统版本为：ubuntu18.04稳定版

1. 例子，输入一个for循环，实用(括号

#!/bin/bash
for i in (1..6)
do
    echo $i
done

2.显示报错信息，bash sh ./ 三种方法都不能运行，vi，vim编辑器都不行

$bash test2.sh
test2.sh: line 2: syntax error near unexpected token `('
test2.sh: line 2: `for i in (1..6)'


$sh test2.sh
test2.sh: 2: test2.sh: Syntax error: "(" unexpected


$./test2.sh
./test2.sh: line 2: syntax error near unexpected token `('
./test2.sh: line 2: `for i in (1..6)'

3. 列出所有shell版本的指向

$ls -l /bin/*sh
-rwxr-xr-x 1 root root 1113504 Apr  5 02:30 /bin/bash
-rwxr-xr-x 1 root root  121432 Jan 25 15:14 /bin/dash
lrwxrwxrwx 1 root root       4 Jun  3 22:05 /bin/rbash -> bash
lrwxrwxrwx 1 root root       4 Jun  3 22:05 /bin/sh -> dash
lrwxrwxrwx 1 root root       7 Jun  3 22:05 /bin/static-sh -> busybox

4.

$su root
Password: 
root@tssys:/home/toucan# dpkg-reconfigure dash
# 选择no

输出显示

Removing 'diversion of /bin/sh to /bin/sh.distrib by dash'
Adding 'diversion of /bin/sh to /bin/sh.distrib by bash'
Removing 'diversion of /usr/share/man/man1/sh.1.gz to /usr/share/man/man1/sh.distrib.1.gz by dash'
Adding 'diversion of /usr/share/man/man1/sh.1.gz to /usr/share/man/man1/sh.distrib.1.gz by bash'

5. 再次查看shell版本，没有改变

root@tssys:/home/toucan# ll /bin/*sh
-rwxr-xr-x 1 root root 1113504 4月   5 02:30 /bin/bash*
-rwxr-xr-x 1 root root  121432 1月  25 15:14 /bin/dash*
lrwxrwxrwx 1 root root       4 6月   3 22:05 /bin/rbash -> bash*
lrwxrwxrwx 1 root root       4 6月   9 18:45 /bin/sh -> bash*
lrwxrwxrwx 1 root root       7 6月   3 22:05 /bin/static-sh -> busybox*

6. 重启电脑

7.测试脚本

原来不能运行的，现在都可以运行了

cat test6.sh
#!/bin/bash
A=(a b c d e)
echo ${A[@]}

no1=1
no2=2
result=$[no1 + no2]
echo $result

a b c d e
3

8. 再次选择Yes，看是否这是影响因素

root@tssys:/home/toucan# dpkg-reconfigure dash
# 选择Yes
Removing 'diversion of /bin/sh to /bin/sh.distrib by bash'
Adding 'diversion of /bin/sh to /bin/sh.distrib by dash'
Removing 'diversion of /usr/share/man/man1/sh.1.gz to /usr/share/man/man1/sh.distrib.1.gz by bash'
Adding 'diversion of /usr/share/man/man1/sh.1.gz to /usr/share/man/man1/sh.distrib.1.gz by dash'

显示结果：
刚刚还能执行的脚本，现在不能执行了

$sh test6.sh
test6.sh: 2: test6.sh: Syntax error: "(" unexpected

9.原因

因为Ubuntu/Debian为了加快开机速度，用dash代替了传统的bash，是dash在捣鬼，解决方法就是取消dash。

dpkg-reconfigure dash
# 选择no